Details

The products entered in the oscpmwin application without a category cannot be found in osCommerce (though they can be displayed in the oscpmwin application).

The products entered in the osCommerce admin interface and then changed in the oscpmwin application to have no category can be found in osCommerce doing a search or in the root level in the admin page.

It seems the first approach does not create a record in the products_to_categories table while the second just set the record to zero.

Fix: when entering a product without category, create the record in the p_to_c table, just setting it to zero.